PARENT SESSION

Behavior 3 -- Session Chair: Sacha Vignieri-- Nelson Hall East, Goodwin Forum

ACTIVITY PATTERNS OF LACTATING SILVER-HAIRED BATS ON ROOST-SHIFT NIGHTS AND NON-SHIFT NIGHTS. Burr J. Betts¹ and Maarten J. Vonhof². ¹ Eastern Oregon University, La Grande, OR, USA; ² York University, Toronto, ON, Canada.

ABSTRACT- Maternity colonies of radio-tagged silver-haired bats (Lasionycteris noctivagans) were monitored to compare nocturnal activity patterns between nights when colonies moved to a new roost site and nights when no roost shift occurred. Secondary goals were to determine at what time roost shifts occurred and the extent of coordination between the shifts of different individuals. The typical activity pattern on non-move nights involved a long first bout away from the roost during which bats often seemed to be night roosting. This first bout was followed by a few bouts in the roost interspersed with additional bouts away from the roost. The typical pattern on roost-shift nights was much more variable. Total time spent in the roosts did not change, but it was divided into more and shorter bouts. The first absent bout was much shorter and bats were rarely detected night roosting. Thus, on roost-shift nights bats appeared to spend more of their absent time foraging, as would be expected for income feeders having the additional energy expense of moving pups to a new roost. The length of time for the entire colony to move varied from about 1-4 hours and moves occurred at various times during the night. Although bats frequently moved back and forth between the old and new roosts, we did not observe bats following colony members. Colony members may learn the location of roosts by eavesdropping on the echolocation calls of colony mates rather than through direct information transfer. It appears that roost shifts were not initiated by a single individual.

KEY WORDS: roost shifts, Lasionycteris noctivagans, activity patterns, silver-haired bats